import XCTest

// Types unicode text into the focused element through the public typeText API,
// avoiding the pasteboard entirely. With replace enabled, the current value
// length is consumed first by prepending that many delete keys so the whole
// replacement happens in one typeText call.
enum TextInput {
    enum TextInputError: Error {
        case typingFailed(String)
    }

    static func type(text: String, replace: Bool, bundleIdentifier: String) throws {
        let application = XCUIApplication(bundleIdentifier: bundleIdentifier)

        var payload = text
        if replace {
            let deleteCount = deletePrefixLength(bundleIdentifier: bundleIdentifier)
            if deleteCount > 0 {
                let deletes = String(repeating: XCUIKeyboardKey.delete.rawValue, count: deleteCount)
                payload = deletes + text
            }
        }

        // Type at the application level so it lands in whatever holds keyboard
        // focus, without resolving a specific element. Compose Multiplatform
        // text fields do not reliably expose hasKeyboardFocus to the query layer.
        // typeText must run on the main thread.
        var caughtError: NSError?
        var completed = false
        runOnMain {
            completed = CompanionRunCatching({
                application.typeText(payload)
            }, &caughtError)
        }
        if !completed {
            throw TextInputError.typingFailed(caughtError?.localizedDescription ?? "unknown")
        }
    }

    private static func runOnMain(_ work: () -> Void) {
        if Thread.isMainThread {
            work()
        } else {
            DispatchQueue.main.sync(execute: work)
        }
    }

    // Sizes the delete prefix for replace. The snapshot does not say which
    // editable field holds keyboard focus (Compose fields never expose
    // hasKeyboardFocus), so the prefix covers the longest editable value on
    // screen: deletes beyond the focused field's content are no-ops at the
    // start of the field, while undersizing would leave residue and silently
    // turn replace into append.
    private static func deletePrefixLength(bundleIdentifier: String) -> Int {
        let elements = Snapshot.elements(bundleIdentifier: bundleIdentifier)
        var longest = 0
        for element in elements {
            guard let type = element["type"] as? String,
                  type == "TextArea" || type == "TextField",
                  let value = element["AXValue"] as? String else {
                continue
            }
            longest = max(longest, value.count)
        }
        return longest
    }
}